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From: gandalf@pro-canaveral.cts.com (Ken Hollis)
Newsgroups: sci.space.shuttle
Subject: Re : SSME's (again...)
Message-ID: <5973@crash.cts.com>
Date: 29 Nov 90 23:16:09 GMT
Sender: root@crash.cts.com
Lines: 60

Greetings and Salutations:

>From: henry@zoo.toronto.edu (Henry Spencer)
>>... because they COULD be made complex.  Computer systems & control

>...  Complexity for complexity's sake is a bug, not a feature.
>Its only function is to keep lots of engineers and technicians employed,
>which drives costs up and up and up.

...and when Canada starts contributing to the Space program, we will be HAPPY
to hear your opinion on cost effectiveness...

>>Pratt & Whitney Turbopumps : Longer life expectancy between changeouts,
>
>...The P&W turbopumps, at the moment, are a prototyping exercise only.
>  There is no commitment to *ever* use them as flight hardware.

There are plans for the incorporation into flight hardware, of course
contingent on the acceptance testing schedules at John C. Stennis Space Center
(SSC) for ?Early 1991? on ME0213.  I don't think ANYBODY would commit to a
part on the promise that it would work, especially NASA.

>>Large throat MCC (Main Combustion Chamber)
>
>Recent progress on this is essentially zero.  And again, there is *no*
>commitment to ever use it for flight hardware; it is being treated as

The Large Throat has been hotfired on engine 0208 (Development Engine) for 310
Seconds.  This modification lowers turbine temps, pump discharge pressure &
preburner chamber pressure to allow normal 109% operation ( or higher).  It
takes years for modifications to get approved, you don't want to rush
something through & screw something else up.

>
>Sorry, I don't give credit for a capability that is not being used because
>of fears that it is unsafe.  They don't run the SSMEs at 109% any more.

On the test stands at SSC, engines ME2010 & ME2014 went through a full 
Performance Certification Cycle.  The wear on the components was more than
expected, while not dangerous, and was not considered to be an effective (or
particularly good) use of the engines.  the engines downgraded back to 104%
nominal usage.  While you are correct that the engines are not run during a
nominal flight at 109%, the flight engines are still tested with short bursts
of up to 113% - 117%.  Development engines are hotfired at 111%.  If you look
up the abort scenarios, there is a requirement for the engines to run at 109%
for an RTLS.
>-- 
>"I'm not sure it's possible            | Henry Spencer at U of Toronto
Zoology
>to explain how X works."               |  henry@zoo.toronto.edu   utzoo!henry
>

I consider this to be "work" and "progress", but since you didn't define the
above, I am sure you will decide for yourself...

Ken Hollis

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